A dangerous cyclone spinning toward the Gulf Coast intensified Thursday to become Tropical Storm Barry.
It's the first tropical storm to threaten the US this year. But before Barry makes landfall -- possibly Saturday in Louisiana -- it'll likely be a full-blown hurricane, meaning its winds will top 74 mph.
But it's not the wind that makes this storm so treacherous. It's the colossal rainfall and massive storm surges.
"This is a life-threatening situation," the National Hurricane Center said. Those in the storm's path should "take all necessary actions to protect life and property from rising water and the potential for other dangerous conditions."
Streets in New Orleans have already turned into lakes after getting pummeled with up to 9 inches of rain Wednesday, three days before the center of the storm is expected to reach land.
And it'll only get worse.
As of 2 p.m. ET, Barry was hurling winds of 40 mph in the Gulf of Mexico, the National Hurricane Center said.
But because Barry is a slow-moving storm -- crawling across the Gulf at just 5 mph -- the system will hover over the same places for a long time, dropping relentless rain and adding to the widespread flooding.
In Grand Isle, Louisiana, the mayor and town council ordered everyone to evacuate Thursday.
"We are expecting a rain fall total that can range from 6" to 10"," they said in a statement. "We will be experiencing unusual high tides that will range more than 3 feet above ground."
Other Gulf states are also at risk. Mississippi, Alabama and the western Florida Panhandle are under the gun for extreme rain, CNN meteorologist Haley Brink said Thursday.
An unprecedented challenge
Barry will inundate Louisiana at a terrible time -- when rivers like the Mississippi are already flooded.
"This is the 258th day of a flood fight on the Mississippi River," Louisiana Gov. John Bel Edwards said Thursday.
Unusually high river levels from severe flooding this year will lead to an unprecedented challenge when Barry makes landfall.
"This is the first time we've had a tropical system with water levels on the river this high," said Jeffrey Graschel, a hydrologist with the National Weather Service's Lower Mississippi River Forecast Center.
In New Orleans, the Mississippi River was more than 16 feet deep on Thursday. At this time of year, it should be more like 6 to 8 feet, Graschel said.
In the coming days, the Mississippi River could crest at 19 feet. That's 1 foot lower than previously forecast. But the bloated river is still risky because the New Orleans is only protected to a height of 20 feet.
In preparation for the onslaught, Louisiana officials have started closing flood gates. The Southeast Louisiana Flood Protection Authority has about 250 flood gates, spokesman Antwan Harris said.
More than 200 flood gates in New Orleans and St. Bernard parishes are expected to be closed by Friday, local media reported.
New Orleans suffered the wrath of the storm's outer bands Wednesday, when up to 9 inches of rain submerged entire neighborhoods.
Resident Dannie P. Davis said she's seen enough and is ready to go. She just doesn't know where yet.
"I am evacuating. The water levels ... were too high for my comfort, and my car nearly flooded," Davis told CNN on Thursday.
"I haven't seen this much rain and flooding before a hurricane in a while. While the evacuation isn't mandatory, I am leaving as a precaution. Who knows what's to come, how and whether the city will able to handle it."
How to prepare
Louisiana's governor warned "no one should take this storm lightly," as 10 to 15 inches of rain could fall within 24 hours between Friday and Saturday.
He declared a state of emergency and urged residents to have a contingency plan for family and pets.
"This is going to be a Louisiana event with coastal flooding and heavy rainfall potentially impacting every part of the state," Edwards said.
And just because the storm might max out as a Category 1 hurricane doesn't mean it won't be destructive. Hurricane categories only denote maximum sustained wind speeds, not rainfall or other factors.
"As we know all too well in Louisiana, low intensity does not necessarily mean low impact," the governor said.
In New Orleans, officials urged residents to:
-- Be ready to stay at home for days or leave at a moment's notice.
-- Have several days' worth of non-perishable food at home.
-- Move outdoor trash cans indoors, since fierce winds could turn heavy objects into projectiles.
In Texas, Gov. Greg Abbott told residents to make plans now.
"Begin preparing your property, your supplies, your lines of communication to your family members," Abbott said. "Begin preparing to know exactly where you need to go if you need to evacuate."
This storm could affect gas prices
Even if you live far from the coast, you could still get hit by the storm in terms of gas prices.
The tropical system is swirling near many of the oil rigs in the Gulf of Mexico. Offshore oil and gas operations in the Gulf are evacuating their facilities, the Bureau of Safety and Environmental Enforcement said.
The companies have evacuated employees from 15 production platforms and four rigs so far. Three of the 20 rigs operating in the Gulf have also moved out of the path of the storm, it said.
Unlike drilling rigs, which typically move from location to location, production facilities stay in the same spot throughout a project's duration.
And even days before landfall. US oil rose above $60 a barrel on Wednesday amid worries that the storm system could derail crude production in the Gulf of Mexico.
CNN's Faith Karimi, Dave Hennen, Monica Garrett, Amanda Watts, Joe Sutton and Christine Sever contributed to this report.